Engine operated portable wood felling saw



Nov. 8, 1955 R. K. A. WIIG ENGINE OPERATED PORTABLE woon FELLING SAW 3 Sheets-Sheet 1 Filed April '7, 1950 \ENEN E .YMMK

w w- An mW/K 4. Mz @"fixa f Nov. 8, 1955 R. K. A. WHG 2,722,923

ENGINE OPERATED PORTABLE WOOD FELLING SAW Filed April '7, 1950 3 Sheets-Sheet 2 Nov. 8, 1955 R. K. A. wuc; 2,722,928

ENGINE OPERATED PORTABLE WOOD FELLING SAW Filed April 7, 1950 3 Sheets-Sheet s United States Patent ENGINE OPERATED PORTABLE wool) FELLING s w R mh K! Aii trsat Wiig, S ar ad o way Application April 7 1950, Serial No. 154,457 Claims priority, appl safion Norway April 9, 1949 The s eh ih en ieh re ers t9 peiteble weed te lhs ew, whi h is eeh s er bl i hte is we ht hen th s ew sefa Th re speeiel at hs te ew of he t pe eem r s hs. an end es eheih e uipped h sew ee h end i ed eleh h Per pher hi it aside plate ent P ate) a d e d s r o he s w ha hs n se e are 19 he a d hem P ee to p eee in ough e re h e95! h e held wit the h nd during the sawing operation, it is of greatest importance to e ee he wei ht is e .Ih s te at ma years f e periments he e er! t he not been pessib e o educe he wei t hthe ehtlythe h est me e s s e the aid e k ew s t e ha e e weigh f mor th n 16 ei'm br he e have h th rt be n sed sm l inte hel-eemhh t eh engine of hernie l 1- H,- nd e se h .ef the ype srbhrete e th electr i nit n T re der m er at s kin li ht enou or preeti el h e, it has hee h es hhy s. simst het hem or a h h hhmber Qt evolht ehs, s! which reason t s een hhessi le te ut l ze heh di e d ese or o b lb a ihe ple heeeh e a teetute h th lest-. iehh e p s o motor is tha the hee is hieetee by mean o h p m at e hiehi h at ig itio an h va ves o h s Phe p do 1 9i h etieh at the hi h numb i t ns r ed for the saw met rs and he me ers o h d p me ts- Ihereter t i hes neve b entheh ht possi e to use mete a other t es. then i h h n rb e e ehd eleet ie i hi eh- 111 this eehhee ieh he i po t nc h s be n e tse d 19. th iee th an nter aleem ust eh ine w th ishhibh has b en u ed for mede sh rsfls bee hse th eese i ha e l eet he m ter of e meter a whieh the lead is eehs n the t me of pe etie on! som seeehsis end th the mal e hciency without importance. That an 'rcraft motor ca be eah e 9 h e eh sht ihe qifi W hwi Pee cen e m mber v er determihih the m me t ef exp sion has been on i e d is leek. sishi ease for o d nary service motors. There has not been thought of h p s b li to u ilis sheh me er for driv n me s ws or ther h n imp emen e esed s .e h y er s, lea m dl n t -l ss. ehe erh hs eehhhe e a ime up to s ver hoursee ih o t r sent ihyehi eh he e eet ie sh ti t h ehd he ue Pum s em ey eihe ed? and h ete i e he Pro ided e het bulb 9 sp eie si n or is eenst heted w th ad u tabl eem ressie chamber As i here pre um d that the h t b lb P iheiple h advan es e er the dies p ineinle the scr t h i subs antia ly eehipr se he pr he e fi st .mehtiened- Fhrthermere, th te is Preyided w h i eren means r securing a eth n seti ieete u de the varying and partly diflicu lt circumstances to which engine operated hand implements are subjected. By replacing a hot bulb systemfor the electric ignition system, the weight of the motor is reduced by about 30%. Beid this gives ree e li t the .eehsh etie e! th other part of the implement. Thus, in motor acee di s t9 he n ehtieh the. vIhhter ey ihs r may be 2,722,928 fiatented Nov. 8, 1955 2 iehhte a ad ant e n h lhh ih dihel i ect n of h aw pla whi has been imp ss b n e m te s ws used so t e eht wh h end s es v b t o s in e a d e ef th s w- According to the present invention, the fuel is sucked in together with the air which is necessary for the explosion. This fuel-air mixture is compressed and caused to explode by contact with the hot bulb.

It m ht. be e ent that p ial ns are eesse y to prevent too early ignition after some time of operation and t r n p s n e e y- Ex er en s ha e ho ha eer e nition s e he e d. by ehh tih he combustion chamber of the hot bulb with the cylinder ye h ne e o e ne h e t en e he c oss section of which causes that a certain "gas compression, for instance the compression necessary to give an explosion at a certain temperature, is vobtained a moment later in e h b lb of t e ihd Du h he t eh of the motor both the cylinder and the channel are cooled from outside, and the hot bulb will have a sufiiciently uniform temperature, to which the moment of ignition i adius d- To keep the hot bulb at a uniform temperature and prevent it from being cooled together with the channel, it has appeared necessary to screen it. For this purpose there is preferably used a jacket of asbestos, covering the outer portion of the hot bulb. Said jacket may be removed when the motor has been completely heated or i ma e meuh Pe ma e t y in d i i h the s rt hea is pp ed to he. ch nne At e a er P ess it m ht be hou th the s a t is r n d m e ff cul by e r ignition, u at h he. yl n er is d and the motor is unloaded, The screening described above is also of importance thereby that the hot bulb keeps he empe a u e e se y for start n some im after the motor has been started, In motors for motor saws it is necessary to have overpressure in the tank for the liquid fuel, because it means a great advantage that the implement may be placed in difierent positions during the work without requiring special manual operations to prevent the fuel from leaking out through the supply hole of the tank or to secure uniform supply of fuel to the meie However, this overpressure involves the drawback that the fuel supply has to be opened and closed at the starting, and at the stopping respectively, of the motor. According to the present invention this drawback is avoided by a device, whereby the overpressure of the motor is conducted through a channel against a membrane or a piston acting on a valve, which, when the motor is out of operation, rests against the nozzle opening with the aid of a spring pressure and closes said opening. At the starting of the motor, the varying pressure of the crankcase causes the piston or membrane to perform a movement which is transmitted to the valve, so that the fuel nozzle is opened. This arrangement also acts as an automatic speed control for the motor. It has turned out, namely, that when the channel is of a certain length and a comparatively small cross section, an increasing number ofrevolutions reduces the average pressure on the pressure side of the membrane with the result that th e ve eh s h th membran th p s on strives to guide the fuel nozzle.

An automatic speed control is also obtainable by treh hii h he ank a e r s h h a a e provided with a pressure valve to a piston placed in a cylinder, which piston is provided with a valve closing the nozzle opening by spring pressure in the position of rest, vi hena pressure arises in the channel, the piston is moved so. that the nozzle is opened. If due to increased e lh ien ef the te h Pr ss re. e s a e in ma mum a rodhs ng on end een ee ed to the Pi t and the other end to the air throttle lever effects a choking of the fuel-air mixture.

If the diesel principle is followed, the compression chamber must have possibilities of expanding responsively to rising cylinder temperature. This is suitably obtained for instance by means of an internally threaded channel with comparatively large diameter leading from the compression chamber, in which a sealing screw may be tightened or loosened.

The main feature of a motor saw according to the invention is that the driving motor is a high speed mixturecompressing combustion motor with hot bulb or selfignition.

To furthermore reduce the weight of the motor saw, the guide plate of the saw chain is constructed with longitudinally extending grooves and as thin as possible. By providing the plate with such grooves it is possible to make it essentially thinner than it must be, if it is made plane.

An embodiment of a motor saw according to the invention and a driving motor pertaining thereto are shown diagrammatically by .way of example in the accompanying drawings, in which Fig. 1 shows the motor saw viewed from the side and Fig. 2 is a plan view of the same. Pig. 3 shows on a larger scale a section through the compression end of the cylinder. Fig. 4 is a section through a fuel control device, likewise on a larger scale, and Fig. 5 is a corresponding construction of a modified embodiment of the control device. Fig. 6 shows a longitudinal section through a safety clutch between the motor and the saw chain, and Fig. 7 shows a clutch part viewed from above.

According to Figs. 1 and 2, the numeral 1 designates the motor proper while 2 is the saw chain which in Fig. l is indicated diagrammatically only. 3 is a bow mounted at the end of the motor facing the saw chain and 4 a handle at the rear end of the motor. 5 is a cross piece intended to rest against a tree during the sawing.

The motor proper comprises the cylinder 11 with cooling flanges 12 and piston 43. 13 designates a tube projecting from the cylinder and communicating internally with the compression end of the cylinder. The outer end of tube 13 is closed to constitute a tubular hot bulb or ignition chamber and the outer portion b of the tube is enclosed by an open tubular jacket 14, preferably of asbestos as previously explained, to retain the heat from the combustion in the engine cylinder. 15 is a fuel tank located on one side of the motor, while 16 is a fuel tank on the other side thereof. The two tanks are interconnected in some appropriate manner. 17 is a pipe leading from the fuel tank 15 to a fuel nozzle 18, by the aid of which a flame can be directed towards the outer portion b of the tube 13. 19 is a valve for controlling the fuel supply to the nozzle 18.

29 is the real fuel supply pipe of the motor and leads to a carburetor 21. 22 is a handle of a member controlling the fuel supply. The carburetor 21 and the member 22 are located on opposite sides of the motor adiacent the handle 4, so that the member 22 is operable by one finger of the hand holding the handle 4. 31 is a so-called guide plate, i. e. an elongated plate serving as guidance for the saw chain. According to the invention the guide plate 31 is made with longitudinal grooves 32. This involves the advantage that the guide plate is stiff even if made essentially thinner than is necessary to obtain sufficient stifiness in a plane plate. 33 designates a saw tooth located on a chain link 34-. The chain links 34 together form an endless chain, which is disposed along the periphery of the guide plate 31 and which at 35 is laid around a chain Wheel not shown here, said chain wheel being driven by the motor. 36 is an arm, which by means of bolts 37 or the like is exchangeably fixed to the guide plate at the outer end thereof. The arm extends approximately in .the plane of the guide plate and perpendicularly to the longitudinal direction thereof, and

serves as support against that side of a tree to be cut, which is opposite to the side against which the saw is resting. It is of importance that this arm is exchangeable, while otherwise the saw would not be usable for cutting trees of larger diameter than the length of the guide plate.

The construction of the motor proper will be described in the following text with special reference to Figs. 3, 4 and 5. As shown in Fig. 3, the compression end of the motor cylinder is adapted with an ignition chamber 44 constituted by the interior of tube 13 mounted at its outer end, which tube protrudes from the cylinder and is screwed into the cylinder head.

The volume of the ignition chamber is suitably dimensioned for determining the motor compression. The diameter of the channel connecting this chamber with the motor cylinder 11 is suitably dimensioned for determining the ignition moment thereby that the portion a in Fig. 3 adjacent the motor cylinder is kept cooled with the aid of an air stream from the cooling fan of the motor, while the outer portion b is not cooled, such portion preferably being insulated by means of the absestos jacket 14 previously referred to and hence will remain hot on account of the explosions. As mentioned before, the portion b is heated by means of a flame at the startmg.

To allow disposition of the motor saw in all planes without any special operations or adjustments, the motor works up a pressure in the tank and the fuel is conducted from the same through a rubber hose, the free end of which is provided with a weight. Further, the fuel is passed on through the pipe 51 to the nozzle 52, the outlet of which into the inlet chamber 53 is closed by the valve 54, see Fig. 4. When the motor piston compresses the air in the crankcase, this pressure is transmitted to the membrane 55 through the channel 56, and the valve 5 admits the fuel to the inlet chamber 53. The spring 57 urges back the valve 54 and closes the fuel nozzle. When the motor has started running, the membrane will give the valve a suitable opening. If the motor is non-loaded, thereby obtaining a higher number of revolutions, there will be formed so much turbulence in the pipe or the channel 56 connecting the crankcase with the membrane housing, that the spring 57 overcomes the pressure exerted by the membrane, the valve 54 will close the fuel supply and the number of revolutions of the motor will fall. Thus, this membrane will act as a speed control. When the motor has run for a time at full load, for instance at felling or cutting, it will be very hot, but because of its piston velocity no preignition will take place.

However, in case the motor is to run slowly, there will be a risk of pro-ignition until the cylinder has cooled down. This can be prevented by choking the pipe sucking in the fuel-air mixture.

Fig. 5 shows how such a choking is effected automatically. In the figure, 61 designates a pipe or channel leading from the crankcase to a cylinder 62, in which a piston 63 is working. The said piston carries a valve head 64 for the fuel supply pipe 65. A narrow channel 66 is arranged in the wall between the cylinder 62 and the air supply pipe. On its opposite side, the piston 63 furthermore carries a rod 67 connected to the lever of a throttle (not shown in the drawing) in the air supply pipe. This device functions in such a manner that at the start of the motor the piston 63 first opens the fuel nozzle 65, whereupon it automatically controls the fuelair supply to the motor. This automatic control is obtained thereby that supply of air through the channel 61 increases with rising number of revolutions, so that the piston 63 is moved to the left. If the number of revolutions decreases, the pressure to the right of the piston will fall because the air leaks out through the channel 66.

It is of great importance that the saw chain is disconnected from the motor if clamped by the tree. For this purpose, some saws use the so-called centrifugal coupling, which operates in such a manner, that the chain is connected when the motor reaches a suitable number of revolutions and is disconnected when the motor is over-loaded or the speed is reduced intentionally. A coupling of this kind demands exact adjustment to prevent wear on the lamellae and besides they are dangerous if the number of revolutions of the motor increases when carried by the cutter between the trees or if the gas control is actuated by a twig or the like, so that the chain is engaged when the cutter is unprepared therefor.

According to the present safety means, accidents are prevented but advantage is taken of the centrifugal force, the motor never being over-loaded or stopped, and no exact adjustment of the coupling is necessary. Besides, one movement of the hand is suflicient to secure that the chain is not connected at all.

The safety connector according to the invention is seen from Figs. 6 and 7. The motor shaft 68 carries a toothed wheel 69 which is rotatably journalled in ball bearings and is in mesh with a drive wheel for the saw chain. The wheel 69 is connected to a case 70, into which is inserted a keyed-up clutch disk 71. The clutch disk is provided with two pivotally journalled cheeks 72 and 73, which, at a certain number of revolutions of the shaft 68 and against spring-action, are swung out towards the inner wall of the case 70 by the centrifugal force, whereby through friction they bring the said case, the wheel 69 and consequently also the saw chain to partake in the rotation.

The checks 72 and 73 are provided with pins 74 and 75 respectively, which at the movement of the checks are displaceable in elongated grooves 76 and 77 respectively in the disk 71. The cheeks are lockable, i. e. they may be prevented from swinging out, for instance by pushing on a conical jacket 78, which is journalled on the shaft 68 and is preferably arranged so as to lock the cheeks when the motor saw is set down on the ground or some other place. The jacket 78 prevents the pins 74 and 75 from sliding in their grooves, whereby the cheeks 72 and 73 are prevented from frictionally engaging the inner side of the case 70. Accordingly, the clutch makes it possible by a single movement of the hand to secure nonconnection of the saw chain. The clutch according to the invention requires no exact adjustment, as there is a con- 6 siderable air gap between the cheeks and the inner side of the case 70.

The motor saw described above starts easily, is reliable and very easy to operate. At the same time it is well up to the purpose, which is of great importance under different working conditions. It should also be mentioned that the saw according to the invention is considerably less expensive to manufacture than the previous motor saws of similar type.

Having now described by invention, what I claim as new and desire to secure by Letters Patent is:

1. In a saw motor of the single cylinder internal combustion type having a crankcase, an intake chamber and a hot bulb for ignition adapted to be connected in driving relation with a saw chain of the endless type, the plane of which is parallel to the motor cylinder, said hot bulb comprising an elongated tubular chamber dimensioned to determine the moment of ignition of the compressed combustible mixture, said chamber being closed at its outer end and having its inner end in communication with said motor cylinder, the inner end portion of said tubular chamber adjacent said motor cylinder being air cooled and the outer end portion of said tubular chamber being non-cooled.

References Cited in the file of this patent UNITED STATES PATENTS 563,051 Nash June 30, 1896 875,256 Gassett Dec. 31, 1907 994,687 Nageborn June 6, 1911 1,878,824 Dodge Sept. 20, 1932 1,891,105 Meyer Dec. 13, 1932 2,080,588 Whittington May 18, 1937 2,091,163 Schweizer Aug. 24, 1937 2,370,556 Mall Feb. 27, 1945 

